Device for separating shrimp from other sea animals

ABSTRACT

A system generally employing a net and an electrical pulse generator that is used for separating shrimp from trash fish, undesirable sea animals and miscellaneous objects. The catch is subjected to an electrical field within the separator which effects only the shrimp. The unwanted portion of the catch not effected by the electrical field passes through the separator and back into the water as it is. No electronarcosis or electrolaxis is produced nor is any of the fish or other undesirables effected in any manner other than possible mechanical diversion, associated with the physical characteristics of the various types and sizes of separators.

United States Patent Metcalf, Jr.

1541 DEVICE FOR SEPARATING SHRIMP FROM OTHER SEA ANIMALS [72] Inventor:

' Pensacola, Fla. 32504 22 Filed: July 6,1970 21 Appl.No.: 52,626

52 us. c| ..L ..43/17.1

Metcalf, Jr ..43/9

Charles B. Metcalf, Jr., 3601 Swan Lane,

[ 1 June 13, 1972 3,561,150 2/1971 Silchenstedt ..43/17.l

FOREIGN PATENTS OR APPLICATIONS 949,531 9/1956 Germany ..43/1 7.1

Primary Examiner-Aldrich F. Medbe Attorney-Hyman l-lurvitz 57 ABSTRACT Asystem generally employing a net and an electrical pulse generator thatis used for separating shn'mp from trash fish, undesirable sea animalsand miscellaneous objects. The catch is subjected to an electrical fieldwithin the separator which effects only the shrimp. The unwanted portionof the catch not effected by the electrical field passes through theseparator and back into the water as it is. No electronarcosis orelectrolaxis is produced nor is any of the fish or other undesirableseffected in any manner other than possible mechanical diversion,associated with the physical characteristics of the various types andsizes of separators.

3 Claims, 2 Drawing Figures PATENTEnJuu 13 I972 v 3,668,801

lNVENT R FIGURE 2 CHARLES E. METCA -F cm.

BACKGROUND OF THE INVENTION It is known that due to the large amount oftrash fish, undesirable sea animals, and miscellaneous objects, etc.,being caught in the trawling net while attempting to capture shrimp, thejob of separating the desired catch from the undesired is laborious andtime consuming. It is further known that shrimp can be made toinvoluntarily propel themselves by applying an electric current throughthe water in which they are located. This current produces an electricalfield of sufficient strength to scare the shrimp but does not produceelectronarcosis or electrotaxis. Various pulse generating devices andelectrode arrangements are available for producing this effect. Forexample, U. S. Pat. Nos. 3,312,011 and 3,491,474 deal specifically withequipment and techniques for scaring of shrimp. 7

If an efficient, practical method of separating the shrimp from the fishwere employed, many hours of manual labor would be saved. In addition,such a device would eliminate the killing of fish and sealife, whichwhen dumped overboard contribute to the contamination of the water andbeaches. By separating the shrimp and fish underwater while still in thenet, the length of time the net can be dragged can be increasedsignificantly; thus adding to the overall efficiency of the operation.At present the physical size of the bag, available power for towing it,limit of the lifting equipment, and damage to the shrimp from beingcrushed'are the limiting factors. It is desirable to drag as long aspossible as the time bringing in the nets and putting them out is wastedand requires manpower for performing. Further, areas which are nowclosed to shrimping because of game fish protection could possibly beopened as nothing but shrimp would be captured by the nets.

It is the intention of this invention to provide such a separator forperforming such a feat.

SUMMARY OF THE INVENTION According to the present invention, fish andshrimp both enter into the net as it is dragged along or near the bottomin the normal manner. The separator panel, which extends from the corkline to the bottom of the net just in front of the bag, is sized suchthat shrimp will pass through easily, but fish and large objects willnot. A trap door is provided on the bottom side of the net just in frontof where the separator panel terminates, thus providing an opening forthe fish and other undesirable objects to pass through. This opening isprovided with an electrode on each of two sides which when excited withpower from a pulse generating device such as described in US. Pat. No.3,491,474 will repel any shrimp that did not work their way through theseparator panel. The electrical field is designed such that it will noteffect fish in any manner. It is specifically tuned and of the correctstrength and repetition rate so as to effect shrimp only. Shrimp, beingrepelled by this field, will become so active that they will forcethemselves back up into the water and through the separator panel andthus into the bag.

' Although this is the preferred arrangement for separation, there couldbe many variations; for example, a section could be inserted between thenet and the bag which could contain electrodes and/or separator mesh oran on-board device could be utilized, providing the shrimp were alivewhen brought on board, The principal object of this invention is theseparation I of shrimp from fish due to the behavior of the shrimp when'stimulated by an electrical field and the non-effect upon the fish whensubjected to the same electrical field.

DESCRIPTION OF THE DRAWINGS The above and still further objects,features and attendant advantages of the present invention will becomeapparent from a consideration of the following detailed description of apreferred embodiment thereof, especially when taken in conjunction withthe accompanying drawin in which:

FIG. 1 is a perspective view of a traw net showing the location of theseparator panel, electrified opening, and associated pulse generatingequipment; and

FIG. 2 is a plan view showing the various sections of the net itself.

DESCRIPTION OF THE PREFERRED EMBODIMENT Reference numeral 1 identifies atrawling net, which normally consists of a wedge-shaped top panel 7 anda similar bottom panel 8, both of which taper to the rear. Suitablyshaped wing panels 6 join the top and bottom panels 7 and 8 and theseterminate in a bag 9. A'headrope 4 equipped with floats is stretchedover the front opening of the trawl l to maintain the net open in thevertical sense. A footrope 5 is stretched along the lower edge of theopening. The ends of the headrope 4 and footrope 5 are connected to theotter boards, or doors, 3 in a conventional manner. The otter boards 3are used to provide a force in the horizontal direction for maintainingthe net in an open position and are connected to the towing lines 2.

Secured to one of the doors 3 is an electrical pulse generating device12 that receives its power either from electrical conductors within thetowing-cable itself 2 or via a separate cable, not shown. The pulsegenerating device l2 delivers power to the electrodes 13 located on eachside of opening 1 1 which will produce an electrical field that effectsshrimp only. All other creatures, objects, etc., will pass throughopening 11 unobstructed. The spacing of the electrodes 13, size of theopening 11, size of the mesh for the separator panel 10, and powerrequirements will be sized in accordance to the ratio of the size of theshrimp to the size of the fish.

While a preferred embodiment of this invention has been disclosed, it isapparent that variation in details of construction which have beenillustrated and described may be resorted to without departing from thespirit and scope of the invention.

I claim:

1. A fish separator, comprising a trawl net having a forward opening forreceiving fish and shrimp into said trawl net, a rearward escape openingin said trawl net, and fish separating means including means supplyingpulses of electricity adjacent said rearward opening, said pulses beingselected to repel shrimp from said rearward opening while having noeffect on fish.

2. The combination according to claim 1 wherein said pulses havevoltages of about to 1% volts and a pulse rate of about 3-6 pulses persecond.

3. A trawling system, comprising a trawl net in the form of a bag havinga forward opening, said bag collecting via said opening a variety ofundesirable sea animals and shrimp, an escape hatch located rearwardlyof said bag, sea animal discriminating means including means forapplying to at least one edge of said escape hatch pulses of electricityof about to 1% volts occurring about 3-6 times per second, whereby saidshrimp are repelled from said escape hatch and do not escape, but saidundesirable sea animals pass through said sea hatch.

1. A fish separator, comprising a trawl net having a forward opening forreceiving fish and shrimp into said trawl net, a rearward escape openingin said trawl net, and fish separating means including means supplyingpulses of electricity adjacent said rearward opening, said pulses beingselected to repel shrimp from said rearward opening while having noeffect on fish.
 2. The combination according to claim 1 wherein saidpulses have voltages of about 3/4 to 1 1/2 volts and a pulse rate ofabout 3-6 pulses per second.
 3. A trawling system, comprising a trawlnet in the form of a bag having a forward opening, said bag collectingvia said opening a variety of undesirable sea animals and shrimp, anescape hatch located rearwardly of said bag, sea animaL discriminatingmeans including means for applying to at least one edge of said escapehatch pulses of electricity of about 3/4 to 1 1/2 volts occurring about3-6 times per second, whereby said shrimp are repelled from said escapehatch and do not escape, but said undesirable sea animals pass throughsaid sea hatch.